Trouble Brewing

A 74-year-old White male presented to our office with complaints of a visual disturbance in his right eye, which began at 9 am that morning, approximately 5 hours prior to the visit, and lasted for 3 hours. He described fogginess in the center of his vision, which seemed to move to the lower right of his field of vision and then disappeared. He also noted a mild headache, which began about 1.5 hours after experiencing visual symptoms.

This individual was an existing patient at our clinic, last seen 1.5 years prior to this visit. He had been monitored for decades as a glaucoma suspect due to moderate, symmetric cupping in the setting of normotensive IOPs and thin corneas (post-LASIK). The patient also had a history of moderate nuclear cataracts OU, hyperlipidemia, hypertension, osteoarthritis, obstructive sleep apnea, and had a BMI of 28. He denied ever smoking or using recreational drugs and reported occasional alcohol use. His family history included a father with cancer and an aneurysm, both unspecified.

CLINICAL FINDINGS

Examination revealed UCVA of 20/25 OU, blood pressure of 165 mm Hg /85 mm Hg, normal pupils with no afferent pupillary defect OU, visual fields full to confrontation OU, and no ocular motility defect. His IOPs were 15 mm Hg OD/17 mm Hg OS via noncontact tonometer. Anterior segment evaluation revealed 1+ nuclear cataracts OU. Dilated eye examination revealed longstanding posterior vitreous detachment OU; moderate optic nerve cupping with no pallor, disc hemes, or edema; and no retinal abnormalities OU.

The patient completed a 30-2 visual field test (Figure 1) with a mild temporal defect noted OD and mild, nonspecific defects noted OS. OCT and fundus photos were obtained, revealing normal fundus appearance, foveal thickness, and contour OU (Figures 2 and 3).

The patient was diagnosed with subjective visual disturbance OD and ocular migraine, with a referral to neuro-ophthalmology for an evaluation in 1 month. He was advised to return to our clinic immediately if there were any changes in his vision.

AN UNEXPECTED CHANGE

The next afternoon was my first encounter with the patient, where he returned with complaints of a static, central visual field defect OD that resembled the Upper Peninsula of Michigan. His UCVA was now 20/200 OD and OS was stable at 20/25. Pupils were marked as normal, with no afferent pupillary defect (more on this later), and other entrance testing was unremarkable. IOPs were measured at 13 mm Hg OD and 12 mm Hg OS via noncontact tonometer. Dilated fundus examination revealed the appearance of subtle whitening in the posterior pole and segmentation of the arterioles exiting the nasal aspect of the optic disc OD. OCT and photos were repeated at this visit, confirming the presence of abnormal foveal contour and inner retinal edema OD, in stark contrast to images obtained the day before (Figures 4 and 5).

A NEW DIAGNOSIS

The patient was diagnosed with a central retinal artery occlusion (CRAO) OD, and I immediately referred him to our main hospital, a nationally recognized stroke center, for an emergent workup.

Hospital staff were notified of the patient’s condition, and he was admitted shortly after his arrival. He received antihypertensive and antiplatelet therapy and a comprehensive evaluation by a team of medical professionals across multiple specialties (Table).

The patient was also seen by the ophthalmology team, where “very mild pallor” and a “subtle cherry-red spot” were noted. Fluorescein angiography of the patient’s right eye revealed normal choroidal filling with delayed filling of the retinal arterial circulation and no evidence of neovascularization. OCT findings revealed abnormal foveal contour and retinal edema OD, consistent with earlier findings.

The patient was hospitalized for 3 days. After analysis of all findings, the etiology of his CRAO was assumed to be from a carotid artery plaque; however, it was determined that carotid endarterectomy was not indicated at this time. Upon discharge, the patient was instructed to continue antiplatelet, antihypertensive, and antihyperlipidemic medications. An implantable loop recorder was also placed to monitor his heart activity. He continues to be observed closely by cardiology, neurology, and our eye care team. His final visual acuity has been stable at 20/200 OD and at age 75 he maintains an active lifestyle.

DISCUSSION

CRAO is a rare, but devastating ophthalmologic emergency with an estimated incidence of one in 100,000 people.^1-4 CRAO has been categorized into four types (in order of most common to least common): nonarteritic permanent, nonarteritic transient, nonarteritic with cilioretinal sparing, and arteritic.^1,5-7 Visual prognosis is often poor, with 80% of patients having a visual outcome of 20/400 or worse.^1,2,8 Patients typically present with acute, unilateral, painless loss of vision, and clinical findings typically include significant reduction in visual acuity, visual field defect, relative afferent pupillary defect, retinal opacity in the posterior pole, cherry-red spot, segmentation of the retinal arterioles, visible arterial emboli, retinal arterial attenuation, retinal and optic disc edema, pallor, and delayed arterial filling on fluorescein angiography.^1,5,7-11

An overwhelming majority of CRAO are caused by emboli from the carotid arteries, with the heart being another source.^1,5,9,12 Emboli are composed of either cholesterol (74%), fibrin (15.5%), or calcium (10.5%).^1,9 Thrombosis and arteritis are other important causes to consider, with the latter being of particular concern due to the risk of significant vision loss in both eyes.^5,9 Data from across multiple studies indicate a higher prevalence in males, ranging between 56% to 70% of observed cases, with average age at time of occurrence being in the mid- to late-60s.⁴ An estimated 78% of patients present with undiagnosed cardiovascular risk factors that are only revealed upon subsequent comprehensive workup, where ipsilateral carotid artery stenosis is present in 40% of patients, but known prior to CRAO occurrence in only 3% of cases.⁴ Hypertension, hypercholesterolemia, heart disease, and tobacco use have all been identified as prominent risk factors for CRAO.^1-6,12,13

Time is critical in CRAO cases; it has been suggested that irreversible retinal damage begins to occur approximately 90 minutes from onset.⁵ CRAO is associated with an increased risk of subsequent stroke; therefore its diagnosis demands an immediate referral for a comprehensive stroke workup and, depending on the patient’s age and other risk factors, testing should include immediate measurement of erythrocyte sedimentation rate, C-reactive protein and platelets to rule out arteritis, carotid ultrasound, echocardiogram, complete blood count with differential, prothrombin time/activated partial thromboplastin time, lipid panel, antinuclear antibody, rheumatoid factor, syphilis testing, and intravenous fluorescein angiography.^{1,2,4,5,8-10,12-14}

Although several treatment options have been suggested, there is no agreed-upon treatment protocol for CRAO, with visual improvement seen in the natural history of the disease often being mistaken for beneficial effects of treatment.⁵ Ocular neovascularization has been identified in a subset of patients with CRAO and while an association remains disputed, it has been recommended that these patients be monitored to rule out ocular neovascularization up to 6 months after diagnosis.^3,5

Our patient initially presented with transient, unilateral vision loss that had resolved by the time he presented to the clinic. Although an afferent pupillary defect was not detected by technicians at the first or second visits, he was dilated before this could be confirmed. For clinics that operate in a similar manner, it is important for technicians to receive sufficient training in order to identify pupillary abnormalities. This case prompted serious discussions about best practices and retraining of technicians to ensure delivery of the highest level of care to our patients.

TAKEAWAYS

Reports of transient vision loss are often difficult to manage and may require a deep dive in order to rule out more serious conditions. In this case, with no observable abnormalities at the first visit, the impending CRAO was misdiagnosed as a subjective visual disturbance and ocular migraine. In reality, this patient was experiencing amaurosis fugax and, considering his age, reported symptoms, and risk factors, a thorough workup was warranted at the initial visit.

Unfortunately, it took another day for findings to manifest and for the patient to be referred for emergent workup. Even when the patient was seen by ophthalmology hours after his second visit, the clinical findings were described as “very subtle,” highlighting the fact that CRAOs do not always present with tell-tale findings. Although visual prognosis is poor in these cases, it is our duty as primary eye care providers to ensure that these patients undergo an immediate and potentially life-saving workup to mitigate the risk of subsequent adverse cardiovascular events.